操作系統是Windows2008R2 ,數據庫是SQL2014 64位。
近階段服務器出現過幾次死機，管理員反饋機器內存使用率100%導致機器卡死。於是做了個監測服務器的軟件實時記錄CPU數據，幾日觀察得出數據如下：
SQL優化方法：
1、查看連接對象
USE master
GO
--如果要指定數據庫就把註釋去掉
SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])='gposdb'
當前連接對象有67個其中‘WINAME’的主機名，‘jTDS’的進程名不屬於已知常用軟件，找到這臺主機並解決連接問題。在360流量防火牆中查看有哪個軟件連接了服務器IP，除之。
2、然後使用下面語句看一下各項指標是否正常，是否有阻塞，正常情況下搜索結果應該為空。
SELECT TOP 10
[session_id],
[request_id],
[start_time] AS '開始時間',
[status] AS '狀態',
[command] AS '命令',
dest.[text] AS 'sql語句',
DB_NAME([database_id]) AS '數據庫名',
[blocking_session_id] AS '正在阻塞其他會話的會話ID',
[wait_type] AS '等待資源類型',
[wait_time] AS '等待時間',
[wait_resource] AS '等待的資源',
[reads] AS '物理讀次數',
[writes] AS '寫次數',
[logical_reads] AS '邏輯讀次數',
[row_count] AS '返回結果行數'
FROM sys.[dm_exec_requests] AS der
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50 AND DB_NAME(der.[database_id])='gposdb'
ORDER BY [cpu_time] DESC
查看是哪些SQL語句佔用較大可以使用下面代碼
--在SSMS裡選擇以文本格式顯示結果
SELECT TOP 10
dest.[text] AS 'sql語句'
FROM sys.[dm_exec_requests] AS der
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50
ORDER BY [cpu_time] DESC
3、如果SQLSERVER存在要等待的資源，那麼執行下面語句就會顯示出會話中有多少個worker在等待
SELECT TOP 10
[session_id],
[request_id],
[start_time] AS '開始時間',
[status] AS '狀態',
[command] AS '命令',
dest.[text] AS 'sql語句',
DB_NAME([database_id]) AS '數據庫名',
[blocking_session_id] AS '正在阻塞其他會話的會話ID',
der.[wait_type] AS '等待資源類型',
[wait_time] AS '等待時間',
[wait_resource] AS '等待的資源',
[dows].[waiting_tasks_count] AS '當前正在進行等待的任務數',
[reads] AS '物理讀次數',
[writes] AS '寫次數',
[logical_reads] AS '邏輯讀次數',
[row_count] AS '返回結果行數'
FROM sys.[dm_exec_requests] AS der
INNER JOIN [sys].[dm_os_wait_stats] AS dows
ON der.[wait_type]=[dows].[wait_type]
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50
ORDER BY [cpu_time] DESC;
4、查詢CPU佔用最高的SQL語句
SELECT TOP 10
total_worker_time/execution_count AS avg_cpu_cost, plan_handle,
execution_count,
(SELECT SUBSTRING(text, statement_start_offset/2 + 1,
(CASE WHEN statement_end_offset = -1
THEN LEN(CONVERT(nvarchar(max), text)) * 2
ELSE statement_end_offset
END - statement_start_offset)/2)
FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
FROM sys.dm_exec_query_stats
ORDER BY [avg_cpu_cost] DESC;
5、索引缺失查詢
SELECT
DatabaseName = DB_NAME(database_id)
,[Number Indexes Missing] = count(*)
FROM sys.dm_db_missing_index_details
GROUP BY DB_NAME(database_id)
ORDER BY 2 DESC;
SELECT TOP 10
[Total Cost] = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0)
, avg_user_impact
, TableName = statement
, [EqualityUsage] = equality_columns
, [InequalityUsage] = inequality_columns
, [Include Cloumns] = included_columns
FROM sys.dm_db_missing_index_groups g
INNER JOIN sys.dm_db_missing_index_group_stats s
ON s.group_handle = g.index_group_handle
INNER JOIN sys.dm_db_missing_index_details d
ON d.index_handle = g.index_handle
ORDER BY [Total Cost] DESC;
找到索引缺失的表，根據查詢結果中的關鍵次逐一建立索引。
做完這些測試，基本能找到問題。
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